There have been conventionally proposed eye condition detection apparatus for detecting the eye condition (e.g., blinking and gaze direction) of a vehicle driver. For example, the eye condition detection apparatus disclosed in Patent Document 1 (i.e., Japanese Patent Document JP-A-H09-21611, also published as U.S. Pat. No. 5,801,763) includes: a light source for illuminating a driver's face; a camera for shooting the illuminated driver's face from the front; and an image processing unit that detects the eye condition from the image of the face picked up by the camera.
Patent Document 1 further discloses that: the light source is disposed in a position away from the camera upward, downward, leftward, or rightward; at this time, the angle formed between the direction of the optical axis of the light source and the shooting direction of the camera is set to approximately 20° to 30° or more. This disposition is for preventing the following from taking place: light projected from the light source is reflected by the lens of a driver's eyeglasses and the reflected light enters the image pickup lens of the camera.
In the Patent Document 1, the present inventors paid attention to that there was only one installation position of the light source for preventing reflected light from an eyeglass lens from entering the image pickup lens of the camera. The present inventors found that in this case, a problem would arise by investigation and experiment.
To explain this problem, FIG. 15 illustrates an example where the direction of the optical axis of a light source 101 is shifted rightward from the shooting direction of a camera 102 (i.e., the direction of the optical axis of a lens of the camera 102). In this case, the direction of the optical axis of the light source 101 is a direction extending from the light source 101 to the estimated position of the head of a driver 100 when he/she sits on the driver's seat. The shooting direction is a direction extending from the camera 102 to the estimated position.
FIG. 16 to FIG. 18 illustrate picked up images of the driver 100's face generated by the camera 102 in this case.
FIG. 16 is an image picked up when the driver 100's face is facing right in front relative to the camera 102. In this case, the side of the face farther from the light source 101 is shaded, and this makes the shaded portion in the image dark. Therefore, it is difficult for the image processing unit to detect the eye on the shaded side. To reduce the influences 103, 104 of the reflection of light from the light source 101 by an eyeglass lens, it is effective to increase the angle formed between the direction of the optical axis of the light source 101 and the shooting direction of the camera 102. However, as the angle formed between the two directions is increased, the above-mentioned adverse effect of shade becomes more noticeable.
FIG. 17 is an image picked up when the driver 100's face is facing toward the side where there is no light source 101 for the camera 102, that is, the face is facing toward the left of the driver 100. In this case, most of the surface of the face is not illuminated with light from the light source and is shaded, and the entire face in the image is darkened. Therefore, it is extremely difficult for the image processing unit to detect an eye.
FIG. 18 is an image picked up by the camera 102 when the driver 100's face is facing toward a direction between the light source 101 and the camera 102. In this case, light is reflected by both the eyeglass lenses, and the reflections 103, 104 are superposed on the eyes. As a result, the image processing unit cannot detect either eye.
In the above example, the direction of the optical axis of a light source is just shifted leftward or rightward from the optical axis of a camera. In this case, it is difficult to detect an eye in almost all the directions in which the driver's face faces. In many periods of time for which the driver is driving a vehicle, it is difficult to carry out the detection of an eye that is an intended purpose of the related art.
FIG. 19 illustrates an example where the direction of the optical axis of a light source 101 is shifted only upward from the shooting direction of a camera 102. That is, the drawing illustrates an example where the light source 101 is disposed away from the camera 102 under the cameral in the vertical direction.
FIG. 20 and FIG. 21 respectively illustrate images picked up by the camera 102 when the driver 100's face in the example of FIG. 19 is facing in the horizontal direction and upward. In these cases, bright spots 103, 104 produced as the result of reflection by eyeglass lenses are shifted from the positions of eyes.
According to the investigation and experiment conducted by the present inventors, however, the following problem arises in the example illustrated in FIG. 19:
FIG. 22 illustrates an image picked up by the camera 102 when the driver 100's face in the example of FIG. 19 is facing in a direction lower than the light source 101. FIG. 23 illustrates an image picked up by the camera 102 when the driver 100's face in the example of FIG. 19 is facing in a direction between the light source 101 and the camera 102. When a face is slightly drooped or turned slightly downward as in these examples, bright spots 103, 104 superposed on both of the eyeglass lenses are produced, and neither of the eyes can be detected. These orientations of a face quite often occur when a driver drives a vehicle or operates equipment in the vehicle compartment. Therefore, in a certain period of time for which the driver is driving the vehicle, neither of his/her eyes can be detected.
A driver 100 often wears his/her eyeglasses in a slightly lower position as illustrated in FIG. 24. In this case, a problem arises even though the optical axis of the light source 101 and the shooting direction of the camera 102 are separated from each other in the vertical direction. When the driver 100 turns his/her face in the horizontal direction as illustrated in FIG. 25, bright spots are produced by reflection by the eyeglass lenses.
As mentioned above, it is difficult to detect an eye in almost all the orientations of the face just by shifting the direction of the optical axis of a light source from the optical axis of a camera in the vertical direction. In many periods of time for which a driver is driving a vehicle, it is difficult to carry out the detection of an eye that is an intended purpose of the related art.